Agronomy Degree Practice Exam

Which type of soil particles are smaller than 0.002 mm in diameter?

1. Silt

2. Clay

3. Loam

4. Sand

The correct answer is: Clay

Soil particles smaller than 0.002 mm in diameter are classified as clay. Clay particles are known for their fine texture and high surface area relative to volume. This small particle size contributes to the unique physical and chemical properties of clay soils, including their ability to retain water and nutrients, which improves soil fertility. The high level of cohesion among clay particles also leads to compactness and the potential for water retention, which is essential in many agricultural practices. In contrast, silt particles range from 0.002 mm to 0.05 mm in diameter, making them larger than clay but still finer than sand. Loam is a mixture of different soil particle sizes, typically consisting of a balance of sand, silt, and clay, which contributes to its desirable properties for supporting plant growth. Sand particles, being the largest among the common soil types, are greater than 0.05 mm in diameter and do not provide the same level of water retention or nutrient-holding capacity as clay. Understanding the classification of soil particles is crucial for effective soil management and crop production strategies.